U.S. patent number 10,809,540 [Application Number 15/827,756] was granted by the patent office on 2020-10-20 for projector having at least four projection light sources and a beam splitter device comprising a polarization beam splitter and projection optics having a beam splitter device.
This patent grant is currently assigned to Jabil Optics Germany GmbH. The grantee listed for this patent is Jabil Optics Germany GmbH. Invention is credited to Eberhard Piehler.
![](/patent/grant/10809540/US10809540-20201020-D00000.png)
![](/patent/grant/10809540/US10809540-20201020-D00001.png)
![](/patent/grant/10809540/US10809540-20201020-D00002.png)
![](/patent/grant/10809540/US10809540-20201020-D00003.png)
United States Patent |
10,809,540 |
Piehler |
October 20, 2020 |
Projector having at least four projection light sources and a beam
splitter device comprising a polarization beam splitter and
projection optics having a beam splitter device
Abstract
The invention relates to a projector (1) and to a projection
optics (30) for a projector (1). In order to be able to operate the
projector (1) as energy-efficiently as possible, it is provided,
according to the invention, that the projector (1) comprises a beam
splitter device (6, 6') having a polarization beam splitter (7,
15), wherein the polarization beam splitter (7) is arranged at an
object-side end (39) of the projection optics (30).
Inventors: |
Piehler; Eberhard (Jena,
DE) |
Applicant: |
Name |
City |
State |
Country |
Type |
Jabil Optics Germany GmbH |
Jena |
N/A |
DE |
|
|
Assignee: |
Jabil Optics Germany GmbH
(Jena, DE)
|
Family
ID: |
56937696 |
Appl.
No.: |
15/827,756 |
Filed: |
November 30, 2017 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20180091785 A1 |
Mar 29, 2018 |
|
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
15088755 |
Apr 1, 2016 |
9860498 |
|
|
|
Foreign Application Priority Data
|
|
|
|
|
Apr 2, 2015 [DE] |
|
|
10 2015 105 107 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04N
9/3164 (20130101); G02B 27/141 (20130101); H04N
9/3167 (20130101); G03B 21/2073 (20130101); G02B
27/283 (20130101); G02B 27/149 (20130101); G02F
1/13355 (20210101); H04N 5/7416 (20130101) |
Current International
Class: |
G02B
27/14 (20060101); H04N 5/74 (20060101); G02F
1/1335 (20060101); H04N 9/31 (20060101); G02B
27/28 (20060101) |
Field of
Search: |
;349/5 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
199 24 096 |
|
Dec 2000 |
|
DE |
|
60 2004 004 581 |
|
Feb 2008 |
|
DE |
|
112013000390 |
|
Sep 2014 |
|
DE |
|
Primary Examiner: Lee; Paul C
Attorney, Agent or Firm: Young Basile Hanlon &
MacFarlane, P.C.
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation of U.S. patent application Ser.
No. 15/088,755, filed Apr. 1, 2016 which claims the benefit of
German Patent Application No 10 2015 105 107.9 filed on Apr. 2,
2015, which is incorporated by reference as if fully set forth.
Claims
What is claimed is:
1. A projector having at least one projection light source and at
least two imaging devices, wherein respectively one projection path
extends from one projection light source, among at least one
projection light source to both of the imaging devices, wherein a
beam splitter device having only one polarization beam splitter is
arranged along the projection path between the projection light
source and the imaging devices and wherein the projector is formed
with at least four projection light sources emitting light of
different wavelengths, in operation, and with at least two beam
splitter devices, wherein the beam splitter devices are arranged to
be able to be illuminated by at least one of the projection light
sources, respectively, and comprise one polarization beam splitter
and at least one dichroic mirror, respectively, wherein the light
reflected by the polarization beam splitter is polarized
differently from the light transmitted through the polarization
beam splitter.
2. The projector of claim 1, wherein the imaging devices are liquid
crystal on silicon imaging devices.
3. The projector of claim 1, wherein the projector comprises at
least two projection light sources from which respectively one
projection path extends to one of the imaging devices in each case,
wherein the beam splitter device is arranged in a crossing region
of the projection paths.
4. The projector of claim 1, wherein the dichroic mirror of a first
one of the beam splitter devices is arranged along the projection
path behind the first beam splitter device, seen from a second one
of the beam splitter device.
5. The projector of claim 4, wherein the dichroic mirror of at
least one of the beam splitter devices comprises a quarter-wave
plate.
6. The projector of claim 1, wherein a portion of the projection
path which extends from one of the beam splitter devices to the
other one of the beam splitter devices extends through an optically
active element.
7. The projector of claim 1, wherein polarizing surfaces of the
polarization beam splitter and reflecting surfaces of the dichroic
mirror are arranged to be crossed with each other.
8. The projector of claim 1, wherein the projector comprises two
projection optics which are adapted to image one of the imaging
devices, respectively, wherein said two projection optics are
provided with one of the beam splitter devices in each case.
Description
FIELD OF INVENTION
The invention relates to a projector having at least one projection
light source and at least two imaging devices, wherein respectively
one projection path extends from the projection light source to
each of the imaging devices. Further, the invention relates to a
projection optics for a projector.
BACKGROUND
Projectors and projections optics of the above-mentioned type are
generally known. In order to be able to illuminate the imaging
devices, known projectors comprise at least one projection light
source for each imaging device. Further, the light of the
projection light source has to be adapted to the demands of the
respective imaging device and, for example, to be polarized. But
the optical components to be used for this purpose, such as
polarization filters, need construction space and cause costs.
Also, about half of the light emitted by the projection light
sources is lost and is not available for the illumination of the
imaging devices.
Thus, the object of the invention is to provide a projector and a
projection optics for a projector which can be constructed in a
compact and cost-efficient manner.
SUMMARY
This object is achieved, for the above-mentioned projector, by a
beam splitter device having a polarization beam splitter, wherein
the beam splitter device is arranged between the polarization light
source and the imaging devices along the projection path. The
object is achieved for the projection optics in that the projection
optics comprises a polarization beam splitter which is arranged at
an object-side end of the projection optics.
By using the beam splitter device comprising the polarization beam
splitter, the light emitted from the polarization light source can
be distributed onto both imaging devices in a differently polarized
manner. In the polarization, not only a part of the light emitted
from the polarization light source is used for the illumination of
the imaging devices like in commonly used polarization filters, but
the light transmitted from the projection light source to the beam
splitter device along the projection path can be distributed
substantially completely onto both imaging devices. Thus, the
projector may be constructed even more compactly because a
projection light source which is weaker compared to known
projectors is sufficient to illuminate the imaging devices, and
thus less waste heat has to be guided out of the projector, without
a decrease of the brightness of the projected image.
The solution according to the invention can be further improved by
different embodiments that are each advantageous alone and can be
combined with one another arbitrarily. These embodiments and the
advantages associated therewith will be discussed hereinafter.
According to a first advantageous embodiment, the imaging device
can be a liquid crystal on silicon (LCoS) device. These imaging
devices can only be operated with polarized light. Nevertheless,
the use of the beam splitter device does not require an increased
construction effort and does not require the use of polarization
filters, the high image quality of the LCoS-imaging device due to
the construction type being maintained unchanged.
Alternatively, the imaging devices can be formed as LCDs or as
micro-mirror devices, so-called DMDs.
The light emitted from the projection light source can be directed
onto the imaging device to be illuminated past the polarization
beam splitter, without etendue-increase.
The projector can be a stereoscopic projector.
Particularly, the projection optics is a projection optics for a
projector according to the invention or of a projector according to
the invention.
The polarization beam splitter splits the light emitted from the
light source into two partial luminous fluxes, wherein respectively
one of the partial luminous fluxes is guided to one of the imaging
devices along a partial luminous flux path or a portion of the
projection path, respectively. The beam splitter device can be
arranged in the beam path before or after a homogenization of the
luminous flux in order to uniformly illuminate the imaging device.
This increases the flexibility of the structure of the projector,
so that it is easier to construct the projector in a compact
manner.
The beam splitter device can be introduced into the projection path
between the at least one projection light source and the imaging
devices before or after bringing together all color components
required for the projection. Alternatively, the beam splitter
device can be additionally used for the color combination.
For example, the projector can comprise at least two projection
light sources, wherein the projection light sources preferably emit
light with different spectrums and emit red/blue or green light,
for example. Respectively one projection path can extend from the
projection light sources to the beam splitter device, wherein the
beam splitter device can be arranged in a crossing region of the
projection paths.
The light of one of the projection light sources is polarized
differently from the other one of the polarization light sources
along the respective projections paths behind the beam splitter
device and particularly between the beam splitter device and one of
the imaging devices. Especially, the light reflected by the beam
splitter device is polarized differently from the light transmitted
through the beam splitter device. An optically active element which
changes the polarization of the light according to its wavelength
can be arranged between the polarization beam splitter and the
imaging device in order for the polarization of the light of both
light sources to be equal when being incident one of the imaging
devices.
According to another preferred embodiment, the projector can be
formed with three projection light sources which emit light of
different wavelengths when in operation. The projection light
sources, for example, can emit red, green or blue light,
respectively. Further, the projector preferably comprises two beam
splitter devices, wherein the beam splitter devices are arranged in
order to be able to be illuminated by at least one of the
projection light sources, respectively. The beam splitter devices
can comprise a polarization beam splitter and a dichroic mirror,
respectively. The dichroic mirror reflects light of selected
wavelengths or wavelength ranges and allows light of other
wavelengths or wavelength ranges to pass through. The dichroic
mirror can be provided with a quarter-wave plate in order to permit
a desired polarization of the light after being reflected at the
dichroic mirror.
The light emitted from one of the light sources is split into both
polarization components by the firstly illuminated polarization
beam splitter. In this case, the light of one of the polarization
components can be directed directly toward one of the imaging
devices through the polarization beam splitter. The light of the
other polarization component can be directed onto the second
polarization beam splitter. It can pass through the polarization
beam splitter to be incident on the dichroic mirror arranged behind
the polarization beam splitter and be reflected back by it. The
back-reflected light is directed toward the second imaging device
through the polarization beam splitter in the second run.
The dichroic mirror of a first of the beam splitter devices can be
arranged along the projection path behind the first beam splitter
device, seen from a second one of the beam splitter device. This
ensures that light guided from one of the polarization light
sources to the second beam splitter device through the first beam
splitter device and then to the dichroic mirror is guided from the
dichroic mirror onto the second beam splitter device and from there
to the imaging device.
In order to be able to appropriately orient the polarization of the
light emitted from one of the projection light sources and guided
from one of the polarization beam splitters to the other one of the
polarization beam splitters, a portion of the projection path which
extends from one of the beam splitter devices to the other one of
the beam splitter devices can extend through an optically active
element. The optically active element turns the direction of the
polarization of the light according to its wavelength.
As an alternative to the dichroic mirror and the polarization beam
splitter being arranged respectively behind one another along the
projection path, polarizing surfaces of the polarization beam
splitter and reflecting surfaces of the dichroic mirror of at least
one of the beam splitter devices, and particularly of each of the
beam splitter devices, can be arranged to be crossed with each
other. For example, the beam splitter devices can be formed as
glass cubes having four parts the surfaces of which are formed as
reflecting or polarizing surfaces and which are connected to each
other and, for example, cemented together. Alternatively, the beam
splitter device can comprise three glass plates or even consist of
them, wherein one of the glass plates is formed as a polarization
beam splitter, for example. The two other ones of the glass plates
can form the dichroic mirror. In this case, the one of the glass
plates can be provided between the two other ones of the glass
plates and arranged in such a way that the result is the crossed
arrangement.
According to embodiments, a (first) projection light source is
oriented in such a way that light emitted from the projection light
source extends along a (first) primary projection path and is
incident on a beam splitter device before reaching one of the
imaging devices. Another (second) primary projection path extends
between a further (second) projection light source and the beam
splitter device and can be oriented in such a way that the light of
the further projection light source is incident on a side of the
polarization beam splitter and the light of the projection light
source is incident on another side of the polarization beam
splitter, and particularly on an oppositely arranged side thereof.
Said primary (first and second) projection paths may cross each
other in the crossing area, wherein the primary projection paths
extend from the respective one of the light sources to the beam
splitting device. Further, said primary projection paths may cross
each other only in the crossing area. In other words, said
projection paths may not cross each other (or overlap or even
partially overlap with each other) in an area between the
respective light source and the beam splitting device.
According to embodiments, an angle between said crossing primary
projection paths may be between 50 and 130.degree. (full circle is
360.degree.), more preferably between 60 and 120.degree., more
preferably between 70 and 110.degree., more preferably between 80
and 100.degree.. According to embodiments, said angle between said
crossing primary projection paths may be 90.degree..
The glass plates are plane-parallel and are, for example, formed of
float glass, and thus the beam splitter device can be manufactured
in a cost-efficient and easy manner.
The projector can comprise two projection optics which image one of
the imaging devices, respectively, and which are provided with one
of the beam splitter devices in each case.
BRIEF DESCRIPTION OF THE DRAWINGS
Hereinafter, the invention will be exemplarily explained based on
exemplary embodiments with reference to the drawings. The different
features of the embodiments can be combined independently from each
other, as has already been explained in the individual advantageous
embodiments.
Shown are:
FIG. 1, a schematic view of an exemplary embodiment of a projector
according to the invention;
FIG. 2, a schematic view of another exemplary embodiment of the
projector according to the invention;
FIG. 3, a schematic view of another exemplary embodiment of the
projector according to the invention;
FIG. 4, a schematic view of another exemplary embodiment of the
projector according to the invention; and
FIG. 5, a schematic sectional view of a first exemplary embodiment
of a projection optics according to the invention for a
projector.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Firstly, the structure and the function of a projector according to
the invention will be described with reference to the exemplary
embodiment of FIG. 1.
Hereinafter, partial luminous flux paths or portions of the
projection paths will be referred to as primary, secondary,
tertiary and quaternary projections paths.
FIG. 1 shows, in a highly schematized manner, a projector 1 having
a projection light source 2 and two imaging devices 3, 4. The
imaging devices 3, 4 are, for example, DMD, LDC or LCOS imaging
devices. The projection light source 2 is, for example, a discharge
lamp and preferably a LED. The projection light source 2 can also
be a light source brought together from several individual light
sources. For example, when in operation, the projection light
source 2 can collectively emit light bundles of red, blue and/or
green light sources, such as LEDs, which are brought together via
at least one dichroic mirror.
The projection light source 2 is oriented in such a way that light
emitted from the projection light source 2 extends along a primary
projection path 5 and is incident on a beam splitter device 6
before reaching one of the imaging devices 3, 4. The beam splitter
device 6 comprises a polarization beam splitter 7 which emits the
light which is emitted from the projection light source 2 along the
primary projection path 5 in a differently polarized manner. The
differently polarized light propagates from the beam splitter
device 6 toward the imaging devices 3, 4 along two secondary
projections paths 8, 9. For example, the secondary projection path
8 extends from the beam splitter device 6 toward the imaging device
3 and the secondary projection path 9 extends toward the imaging
device 4. Preferably, the light is polarized linearly by the
polarization beam splitter 7, wherein the polarization direction of
the light propagating along the secondary projection path 8 is
oriented vertically to a polarization direction of the light
propagating along the secondary projection path 9.
The light emitted from the beam splitter device 6 can be incident
on an apparatus 10, 11 for orienting and/or homogenizing the
luminous flux before reaching one of the imaging devices 3, 4.
Particularly, the projector 1 can comprise an apparatus 10, 11 for
each imaging device 3, 4 which is arranged between the polarization
beam splitter 7 and one of the imaging devices 3, 4, so that a
desired orientation and a maximally homogeneous distribution of the
light reaching the imaging devices 3, 4 are ensured.
Additionally, the beam splitter device 6, and particularly the
polarization beam splitter 7 thereof, can be arranged in the beam
path before or after the homogenization of the luminous flux for
the uniform illumination of the imaging devices 3, 4.
FIG. 2 schematically shows another exemplary embodiment of the
projector 1 according to the invention. Like reference numerals are
used for elements the function and/or structure of which is the
same as the function and/or structure of the elements of FIG. 1.
For brevity's sake, hereinafter only the differences from the
exemplary embodiment of FIG. 1 are illustrated.
The projector 1 of the exemplary embodiment of FIG. 2 comprises a
further projection light source 12 in addition to the projection
light source 2. For example, the further projection light source 12
can emit light of another wavelength range than the projection
light source 2. One of the projection light sources 2, 12 can, for
example, be configured to emit light of two base colors, and the
other one of the projection light sources 2, 12 can be configured
to emit a remaining base color. Base colors are red, green and
blue, for example. Further, the projector 1 can comprise three
projection light sources, wherein each of the projection light
sources is configured to emit one of the base colors. When more
than three base colors or additional white light are used for the
projection, the projector 1 can comprise one projection light
source for each base color and for the white light.
The projection light sources 2, 12 can be arranged on different
sides of the beam splitter device 6. A primary projection path 13
extending between the further projection light source 12 and the
beam splitter device 6 thus can be oriented in such a way that the
light of the further projection light source 12 is incident on a
side of the polarization beam splitter 7 and the light of the
projection light source 2 is incident on another side of the
polarization beam splitter 7, and particularly on an oppositely
arranged side thereof.
The light emitted from the projection light sources 2, 12 is
directed in a polarized manner toward the imaging devices 3, 4
along the secondary projection paths 8, 9. Alternatively, the
projection light sources 2, 12 can be arranged on a side of the
beam splitter device 6, so that the light emitted from both
projection light sources 2, 12 is incident on the same side of the
polarization beam splitter 7. Thus, the beam splitter device 6 can
be introduced into the beam path of the projector 1 extending along
the projection paths 5, 8, 9, 13 before or after bringing together
all color components. Further, the beam splitter device 6 can also
be used for the color combination.
When the projection light sources 2, 12 are arranged on different
sides of the polarization beam splitter, the light emitted from the
projection light source 2 extends along the secondary projection
paths 8, 9 with a polarization different from that of the light
emitted from the further projection light source 12. But if the
light of the projection light sources 2, 12 is be guided to the
imaging devices 3, 4 with the same polarization, an optically
active element is to be provided between the polarization beam
splitter 7 and both imaging devices 3, 4, respectively, which
changes the polarization according to the wavelength and
selectively turns only the polarization direction of the light of
one wavelength or of one wavelength range about 90.degree., for
example.
FIG. 3 schematically shows another exemplary embodiment of the
projector according to the invention. Like reference numerals are
used for elements the function and/or structure of which is the
same as the function and/or structure of the elements of the
preceding exemplary embodiments. For brevity's sake, hereinafter
only the differences from the preceding exemplary embodiments are
illustrated.
FIG. 3 shows the projector 1 having both projection light sources
2, 12 as well as a third projection light source 14. Each of the
projection light sources 2, 12, 14 preferably is configured to emit
light of another wavelength range than the other ones of the
projection light sources 2, 12, 14 when the projector 1 is in
operation. The light emitted in operation from the projection light
sources 2, 12 firstly is guided toward the imaging device 3 via the
polarization beam splitter 7. Further, the light of the projection
light sources 2, 12 is guided from the polarization beam splitter 7
to another polarization beam splitter 15 and from there to the
imaging device 4. The light of the third projection light source 14
is guided from the projection beam splitter 15 onto the imaging
device 4 and to the projection beam splitter 7 and from there onto
the imaging device 3.
Hereinafter, the way of the light emitted in operation from the
individual projection light sources 2, 12, 14 along the projection
paths will be described.
The light emitted in operation from the projection light source 2
is guided toward the polarization beam splitter 7 along the primary
projection path 5. On its way to the polarization beam splitter 7,
the light emitted from the projection light source 2 is incident on
a color-selective or dichroic mirror 16 which is arranged between
the projection light source 2 and the polarization beam splitter 7
along the primary projection path 5. The dichroic mirror 16 is
configured to let pass the light emitted in operation from the
projection light source 2. The light emitted from the projection
light source 2 is not polarized or is circularly polarized at least
between the projection beam splitter 7 and the dichroic mirror 16.
Particularly, the projection light sources 2, 12, 14 are configured
to emit light in a non-polarized manner.
When the light emitted from the projection light source 2 along the
primary projection path 5 is incident on the polarization beam
splitter 7, the polarization beam splitter 7 guides a part of the
light to the imaging device 3 along the secondary projection path
8. The part of the light guided to the imaging device 3 is linearly
polarized in a predefined direction. Another part of the light
guided to the polarization beam splitter 7 is transmitted by the
polarization beam splitter 7 and guided to the polarization beam
splitter 15. This part of the light is also linearly polarized,
wherein its polarization direction is vertical to the polarization
direction of the light reflected by the polarization beam splitter
7 toward the imaging device 3. Thus, a tertiary projection path 17
extends between the projection beam splitters 7, 15. An imaging
optics 18 can be arranged along the tertiary projection path 17 for
imaging the partial luminous flux guided from the polarization beam
splitter 7 to the polarization beam splitter 15.
When both polarization beam splitters 7, 15 are formed with
substantially identical optical characteristics, the polarization
beam splitter 15 lets pass the light guided thereto along the
tertiary projection path 17 without reflecting significant portions
thereof. Thus, the tertiary projection path 17 extends through the
polarization beam splitter 15. After the tertiary projection path
17 has passed through the projection beam splitter 15, the tertiary
projection path 17 ends at another color-selective dichroic mirror
19. The dichroic mirror 19 is configured to reflect the light
emitted from the projection light source 2. In order to be able to
guide the light reflected by the dichroic mirror 19 onto the
imaging device 4 by the polarization beam splitter 15, it may be
necessary to change the polarization thereof. For example, it may
be necessary to change the polarization direction of the light. For
this purpose, the dichroic mirror 19 can be equipped accordingly on
the side 20 thereof facing the polarization beam splitter 15. For
example, the dichroic mirror 19 can be provided with a quarter-wave
plate which is formed as a layer applied on the mirror 19 or as a
layer stack. The light reflected by the dichroic mirror 19 passes
through the quarter-wave plate two times, i.e., a first time before
the reflection and another time after the reflection at the
dichroic mirror 19. Thus, the quarter-wave plate acts as a
half-wave plate and can turn the polarization direction of the
reflected light about 90.degree., for example, so that the
polarization beam splitter 15 can guide the light reflected by the
dichroic mirror 19 substantially completely to the imaging device 4
along the secondary projection path 9.
The light guided from the further projection light source 12 to the
polarization beam splitter 8 along the primary projection path 13
is split into two differently polarized partial luminous fluxes by
the polarization beam splitter 7, wherein a first one of the
partial luminous fluxes is guided to the imaging device 3 along the
secondary projection path 8 and, for this purpose, is transmitted
by the polarization beam splitter 7. The partial luminous flux of
the light emitted in operation from the projection light source 12
which is reflected by the polarization beam splitter 7 is guided to
the polarization beam splitter 15 along another tertiary projection
path 17'.
When both projection beam splitters 7, 15 present identical optical
characteristics, the projection beam splitter 15 substantially
completely reflects the light reaching it along the tertiary
projection path 17' toward another color-selective dichroic mirror
21. Alternatively, the dichroic mirror 21 can be a
non-color-selective mirror if no light of one of the projection
light sources 2, 12, 14 is to be transmitted by the mirror 21. The
light reflected by the mirror 21 is transmitted to the imaging
device 4 by the polarization beam splitter 15. In order for the
polarization beam splitter 15 to let pass and to not reflect the
light reflected by the mirror 21, the mirror 21 also comprises a
quarter-wave plate at the side 22 thereof facing the polarization
beam splitter 15 which is formed as a layer or as a layer stack on
the mirror 21, for example. In this case, the light reflected
toward the mirror 21 by the polarization beam splitter 15 passes
through the quarter-wave plate two times, so that the polarization
direction thereof can be turned about 90.degree., for example.
Thus, the light reflected by the mirror 21 can readily reach the
imaging device 4 through the projection beam splitter 15.
The light emitted in operation by the third projection light source
14 is firstly incident on the dichroic mirror 19 on its way to the
polarization beam splitter 15 along a primary projection path 23.
The dichroic mirror 19 is configured to transmit the light emitted
from the projection light source 14. When the light emitted in
operation from the projection light source 14 is non-polarized, the
polarization of the light does not change after the passage through
the mirror 19. The beam splitter 15 splits the light emitted in
operation from the projection light source 14 into two partial
luminous fluxes, wherein a first partial luminous flux is guided to
the imaging device 4 along the secondary projection path 9. The
partial luminous flux which is guided to the imaging device 4 thus
is reflected by the polarization beam splitter 15. The remaining
part of the light is guided to the polarization beam splitter 7
along another tertiary projection path 24. Again, an imaging optics
can be arranged along the tertiary projection path 24.
If the tertiary projections paths 17, 17', 24 overlap, it may be
sufficient to provide a single imaging optics 18. Alternatively, at
least one of the tertiary projection paths 17, 17', 24 can extend
in order to be spaced apart from at least another one of the
tertiary projection paths 17, 17', 24 and can be imaged by a
separately formed imaging optics.
The partial luminous flux propagating along the tertiary projection
path 24 can pass through the polarization beam splitter 7 due to
its polarization without being significantly reflected, when the
polarization beam splitters 7, 15 are both formed with comparable
optical characteristics. The tertiary projection path 24 extends
through the polarization beam splitter 7 to the dichroic mirror 16
which is configured to reflect the light emitted in operation from
the projection light source 14. In order to be able to guide the
light reflected by the mirror 16 to the imaging device 3 and in
order for it to be reflected by the projection beam splitter 7, the
mirror 16 can also be configured, on the side 25 thereof facing the
polarization beam splitter 7, to change the polarization of the
light to be reflected by the mirror 16. Particularly, the mirror 16
can be provided with a quarter-wave plate on its side 25 which is
applied as a layer or as a layer stack on the side 25, for example.
The light to be reflected, in turn, passes through the quarter-wave
plate two times, so that the quarter-wave plate functions as a
half-wave plate and changes the polarization direction of the
reflected light.
So, respectively one primary projection path 5, 13, 23 extends from
the projection light sources 2, 12, 14 to the respectively nearest
polarization beam splitter 7, 15. Respectively one secondary
projection path 8, 9 extends from the projection beam splitters 7,
15 to one of the imaging devices 3, 4. Tertiary projection paths
17, 17', 24 extend between the polarization beam splitters 7, 15.
Here, the tertiary projection paths 17, 17', 24 can extend to one
of the dichroic mirrors 16, 19, 21 through the polarization beam
splitter 15, 17 receiving the light from the respectively other
polarization beam splitter 7, 15. Quaternary projection paths,
which, for clarity's sake, are not indicated by a reference
numeral, extend from the dichroic mirrors to respectively one of
the polarization beam splitters 7, 15. The dichroic mirrors 16, 19,
21 and the polarization beam splitters 7, 15 can form beam splitter
devices 6, 6' and be integrally operable, for example.
FIG. 4 shows a schematic view of another exemplary embodiment of
the projector 1 according to the invention. Like reference numerals
are used for elements the function and/or structure of which is the
same as the function and/or structure of the elements of the
preceding exemplary embodiments. For brevity's sake, hereinafter
only the differences from the preceding exemplary embodiments are
illustrated.
The projector 1 of the exemplary embodiment of FIG. 4 is
substantially the same as the projector 1 of the exemplary
embodiment of FIG. 3. Particularly, the projector 1 of the
exemplary embodiment of FIG. 4 comprises three projection light
sources 2, 12, 14 of two imaging devices 3, 4 and two beam splitter
devices 6, 6'. However, the beam splitter devices 6, 6' of the
exemplary embodiment of FIG. 4 are different from the beam splitter
devices 6, 6' of the exemplary embodiment of FIG. 3.
The beam splitter devices 6, 6' of FIG. 4 are formed with a
polarization beam splitter 7, 15 and a dichroic mirror 16, 26,
respectively, wherein the polarization beam splitters 7, 15 and the
dichroic mirrors 16, 26 of each of the beam splitter devices 6, 6'
are arranged to be crossed with one another. For example, the
polarization beam splitters 7, 15 can be formed as a continuous
glass and/or plastic plate, respectively, which is equipped to
divide incident light into partial luminous fluxes of different
polarizations. The dichroic mirrors 16, 26 can comprise two glass
and/or plastic plates, respectively, which are arranged to be
aligned with one another. The polarization beam splitter 7, 15 can
be arranged between the two parts of the dichroic mirror 16, 26.
The plates forming the dichroic mirrors 16, 26 can be equipped and
be coated, for example, to reflect or transmit light in a
color-selective manner.
Alternatively, the polarization beam splitters 7, 15 and the
dichroic mirrors 16, 26 can be provided on surfaces arranged within
a, for example, cube-shaped beam splitter device 6, 6'. The
cube-shaped beam splitter device 6, 6' can comprise four segments,
for example, or even consist of them, the inner surfaces of which
extend along diagonals of the cube-shaped beam splitter device 6,
6', for example. The surfaces of the segments can be alternately
formed as a polarization beam splitter or as a dichroic mirror and
be correspondingly coated, for example, along a circumferential
direction of the beam splitter device 6, 6'.
The projection light sources 2, 12 are arranged in such a way that
their light firstly is incident on the beam splitter device 6
adjacently arranged in FIG. 4. The light of the projection light
source 2 is reflected from the beam splitter device 6 toward the
imaging device 3 and transmitted toward the beam splitter device
6'. The light emitted in operation from the projection light source
12 firstly is incident on the beam splitter device 6 from which it
is reflected toward the other beam splitter device 6' and
transmitted to the imaging device 3. Thus, the light of the
projection light sources 2, 12 guided to the beam splitter 6' can
be polarized differently as shown in the exemplary embodiment of
FIG. 3. In order for the light of both projection light sources 2,
12 to be reflected by the dichroic mirror 26 toward the imaging
device 4 and to be guided at least partially through the
polarization beam splitter 15 before, the projector 1 of the
exemplary embodiment of FIG. 4 comprises an optically active
element 28 which changes the polarization of the light in a
color-selective manner. Particularly, the optically active element
28 turns the polarization direction of the light of the projection
light source 12 reflected by the polarization beam splitter 7 about
90.degree., so that the partial luminous flux reflected by the
projection beam splitter 7 of the light emitted in operation from
the projection light source 12 can traverse the polarization beam
splitter 15 substantially without being reflected.
The light emitted in operation from the projection light source 14
is split into two partial luminous fluxes by the polarization beam
splitter 15, wherein one of the partial luminous fluxes is
reflected to the imaging device 4 and the other one is transmitted
to the beam splitter device 6 through the polarization beam
splitter 15 and the mirror 26. The optically active element 28 can
be configured to let pass the transmitted partial luminous flux of
the light emitted from the projection light source 14 unchanged.
Alternatively, the partial luminous flux can be guided to the beam
splitter device 6 past the optically active element 28. When the
polarization beam splitters 7, 15 are formed with comparable
optical characteristics, the polarization beam splitter 7 allows
for transmitting the light which has passed the polarization beam
splitter 15, so that it is reflected onto the imaging device 3 by
the dichroic mirror 16.
The dichroic mirrors 16, 26 of the exemplary embodiment of FIG. 4
can be formed without quarter-wave plates or coatings having such a
function. The beam splitter device 6 can comprise the polarization
beam splitter 7 and the dichroic mirror 16, and particularly
consist thereof, wherein the beam splitter device 6 can be
constructed in a plate-shaped or in a cube-shaped manner. The beam
splitter device 6' can additionally comprise the optically active
element.
FIG. 5 schematically shows a sectional view of a first exemplary
embodiment of a projection optics according to the invention for a
projector 1.
The projection optics 30 is illustrated with one of the imaging
devices, and particularly, is exemplarily illustrated with the
imaging device 3. The polarization beam splitter 7 by which the
imaging device is illuminated and imaged is a part of the
projection optics 30. The imaging device 3 reflects the incident
light back onto the polarization beam splitter 7 which reflects the
light toward a first partial optics 31 of the projection optics 30.
The first partial optics 31 preferably has a positive refractive
power. A second partial optics 32 of the projection optics 30 which
preferably has a negative refractive power is downstream of the
partial optics 31.
A bending device 33, for example, a prism or a mirror, is arranged
between the two partial optics 31, 32, so that the projection
optics 30 can be constructed in a space-saving manner. The bending
preferably is performed about a long axis of the image field which
has an aspect ratio of 2:1 or less, for example, and preferably of
16:10 or 21:9.
The first partial optics 31 comprises at least two optical
component assemblies 34, 35, for example, wherein the first optical
component assembly 34 is connected between the polarization beam
splitter 7 and the second component assembly 35. The first optical
component assembly 34 has a positive refractive power, for example.
The second optical component assembly 35 includes at least one
cemented member.
The second partial optics 32 also comprises at least two optical
component assemblies 36, 37, wherein the first optical component
assembly 36 is connected between the bending device 33 and the
second optical component assembly 37. The first optical component
assembly 36 preferably is formed with a negative refractive power.
The second optical component assembly 37 comprises at least one
cemented member.
When the bending between both partial optics 31, 32 is realized
with a prism, the entry surface and the exit surface of the prism
can also be provided with an optical effect and with convex or
concave surfaces, for example. At least one positive lens of the
first partial optics 31 can comprise aspheric surfaces. A negative
lens of the second partial optics 32 can comprise aspheric
surfaces. Viewed from the polarization beam splitter 7 in a
projection direction R along the projected light, the light is
guided onto an exit surface 38. The projected image is quasi formed
in the infinite or as a virtual image at a greater distance from
the projection optics 32. Since the projection optics 30 images the
imaging device 3, the projection beam splitter 7 is arranged at an
object-side end 39 of the projection optics 30.
The image can be guided from the exit surface 38 into at least one
eye of a viewer and, for example, can be reflected into it. For
this purpose, further components can be provided which direct the
image of the exit surface 38 to the viewer.
The projector 1 can comprise two projection optics 30 which image
one of the imaging devices 3, 4, respectively, and comprise one of
the beam splitter devices 6, 6', respectively. Such a projector 1
can be a stereoscopic projector.
* * * * *